The present invention relates generally to a dyed polyamide articles (e.g., fibers, yarns, fabrics and the like) having markedly improved wetfastness properties. In particular, the present invention relates to dyed polyamide 6 articles and methods of making the same which result in improved wetfastness and colorfastness properties.
Polyamide (nylon) polymers such as, for example, polyamide-6 and polyamide-6,6 are commonly used in the production of fibers and yarns for elastic fabrics, especially swimwear. When textile fibers and yarns made of polyamide-6 are used for elastic fabric applications, they exhibit a wetfastness problem. More specifically, elastic fabrics made from polyamide-6 have a poorer dye bleed performance in water and a poorer colorfastness to laundering and perspiration than elastic fabrics made from polyamide-6,6.
Broadly, the present invention improves the wetfastness properties of polyamide-6 articles and decreases the bluing of Acid Red 52 upon aftertreatment and laundering while reducing processing costs (e.g., by reducing the energy and time of such treatments as compared to conventional polyamide-6 fibers). More specifically, the present invention is embodied in polyamide-6 articles having dramatically improved dye bleed and perspiration performance characteristics, as well as reduced color change of fluorescent dyed polyamide-6.
These improvements are achieved according to the present invention by modifying conventional dyeing and aftertreatment conditions. That is, conventional temperatures used for dyeing and the aftertreatment of polyamide-6 yarns are typically about 100xc2x0 C. and 77xc2x0 C., respectively. In contrast, the dyeing and aftertreatment procedures of this invention are carried out at about 80xc2x0 C. or lower (e.g., between about 70xc2x0 C. to about 80xc2x0), and about 50xc2x0 C. or lower (e.g., between about 20xc2x0 C. to about 50xc2x0 C.), respectively. Bath ratios of between about 15:1 to about 20:1 are employed with the polyamide-6 article being retained in the bath sufficient to achieve at least about 75% dye uptake, and more preferably between about 75% to about 80% dye uptake.
These and other aspects and advantages will become more apparent after careful consideration is given to the following detailed description of the preferred exemplary embodiments thereof.
To promote an understanding of the principles of the present invention, descriptions of specific embodiments of the invention follow, and specific language is used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is intended by the use of this specific language and that alterations, modifications, equivalents, and further applications of the principles of the invention discussed are contemplated as would normally occur to one of ordinary skill in the art to which the invention pertains.
The polyamide-6 that may be employed in the practice of the present invention may be made by hydrolytically polymerizing polyamide-6 forming monomers such as, for example, poly(epsilon-caprolactam) in the presence of water and a carboxylic acid chain regulator. The carboxylic acid chain regulator is added in an amount ranging from about 0.01 to about 0.50 weight percent. Preferably, the amount of carboxylic acid chain regulator added is between about 0.05 and about 0.40 weight percent. Water is preferably used as a polymerization initiator. The amount of water used as an initiator may vary but is typically about 0.40 weight percent based on the weight of the polyamide-6 forming monomers.
The polyamide 6 may be formed into various shaped articles, such as, for example, fibers, yarns, textile fabrics, and the like. Fibers may be formed by subjecting the polyamide-6 to any conventional fiber-forming process such as, for example, that disclosed in U.S. Pat. No. 4,983,448 to Karageorgiou and U.S. Pat. No. 5,487,860 to Kent et al., each being expressly incorporated hereinto by reference. Similarly, fabrics may be formed by subjecting the polyamide-6 to any conventional fabric-forming process such as, for example, the process disclosed in U.S. Pat. No. 4,918,947 to Speich, the entirety of which is expressly incorporated hereinto by reference.
The polyamide-6 fibers and/or fabric may then be subjected to dyeing and aftertreatment in accordance with the present invention. The polyamide-6 articles may be dyed with conventional dyes used to dye polyamides, for example, metallized and non-metallized acid dyes. Dyeing may occur in fiber form such as in stock dyeing of filament staple, tow, tops, or sliver. Dyeing may also occur in fabric form such as woven, non-woven, or knitted goods or in garment form. The dyestuffs are preferably non-complexed acid dyes or 1:2 metal-complexed acid dyes prepared with chrome, iron, cobalt, copper, aluminum, or any transition metal.
The following general conditions are exemplary and not intended to be limiting. A dyebath is prepared at a volume equal to between about fifteen to about twenty times the weight of the articles to be dyed. Processing chemicals are added, including a chelating agent to prevent the deposition or complexing of metal ions in hard water, a dye leveling agent, and, in the case of metallized acid dyes, an acid donor to slowly lower the dyebath pH. The dyestuff is added, and the dyebath pH is adjusted to between about 5 and about 7 for acid dyes and to between about 8 and about 10 for metallized acid dyes. The dyebath solution is heated to the desired temperature, typically less than about 82xc2x0 C. (180xc2x0 F.), and typically between about 70xc2x0 C. (158xc2x0 F.) and about 80xc2x0 C. (176xc2x0 F.), at a rate of from about 0.5xc2x0 C. to about 3.0xc2x0 C. per minute and is held at that temperature for about 30 minutes to about 60 minutes. The dyebath is then cooled or emptied, and the articles are thoroughly rinsed with fresh water. The dyed articles are then aftertreated in a bath containing no added dye and dried in a tumble drier or in a vertical oven such as a Tenter or are passed over heater cans. The dyed articles may then be optionally heatset to improve dimensional stability.
A further understanding of this invention will be obtained from the following non-limiting Examples.